1. Field of the Invention
The present invention relates to a transverse sealing mechanism for a bag-manufacturing and packaging machine. More particularly, the present invention relates to transverse sealing mechanism for a bag-manufacturing and packaging machine that makes bags by sealing a tubular packaging material longitudinally and transversely while also filling the bags with items to be packaged.
2. Background Information
There exist longitudinal bag packaging machines that make bags while filling the bags with a food product or other packaging items.
One example is a bag-manufacturing and packaging machine called a “pillow packaging machine.” In this machine, a packaging material, which is a sheet-like film, is formed into a tubular form using a tube called a “former.” Then, overlapping longitudinal edges of the tubular packaging material are thermally sealed by a longitudinal sealing mechanism. The tubular packaging material, which will become the bag, is then filled with items to be packaged through the tube. Finally, a transverse sealing mechanism located below the tube thermally seals a portion of the tubular packaging material that straddles the top part of the current bag and the bottom part of the next bag, and severs the thermally and transversely sealed portion across its middle with a cutter. In other words, this kind of pillow packaging machine executes two operations as just described: the making of bags and the filling of the bags with items to be packaged.
The transverse sealing mechanism used in this kind of bag-manufacturing and packaging machine often includes a mechanism in which a pair of sealing parts called “sealing jaws,” which are arranged so as to face each other across the conveyance path of the tubular packaging material, are pressed together so as to thermally weld the tubular packaging material. When the sealing jaws are arranged such that they undergo mere horizontal linear reciprocal motion, the packaging material can only be sealed at one position. As a result, since the conveyance of the tubular packaging material must be stopped for the period of time required to make the seal, the sealing jaws are often moved along a D-shaped annular path. By making the sealing jaws follow the tubular packaging material as it is conveyed in this way, this kind of bag-manufacturing and packaging machine can secure longer thermal sealing times without stopping the conveyance of the tubular packaging material.
In order to increase the bag packaging speed and increase the number of bags that can be produced per unit time, there are structures adopted recently, in which the transverse sealing mechanism has left and right units that are arranged opposite each other so as to sandwich the conveyance path of the tubular packaging material. In this new structure, each unit is provided with a plurality of sealing jaws that are revolved through an annular path. For example, Japanese Patent Application Publication No. 2001-382895 describes a transverse sealing mechanism having a left sealing jaw revolving unit and a right sealing jaw revolving unit, each provided with two sealing jaws. In other words, there are two pairs of left-right sealing jaws, both of which execute transverse sealing of the tubular packaging material. As a result, the bag packaging capacity is double that of a conventional bag-manufacturing and packaging machine that has one pair of sealing jaws per unit (left and right), when operating at the same revolution velocity.
Bag packaging machines like that described in the aforementioned publication are often used to manufacture bags of the same size continuously. However, there are times when bags of differing sizes must be manufactured. In order to accommodate production of larger bags, it is necessary to increase the spacing between the left and right units of the transverse sealing mechanism. As a result, the overall size of the bag-manufacturing and packaging machine also increases.
In view of the above, there exists a need for bag-manufacturing and packaging machine transverse sealing mechanism which overcomes the above mentioned problems in the prior art. This invention addresses this need in the prior art as well as other needs, which will become apparent to those skilled in the art from this disclosure.